Methods of depositing materials over substrates, and methods of forming layers over substrates

ABSTRACT

The invention includes methods of utilizing supercritical fluids to introduce precursors into reaction chambers. In some aspects, a supercritical fluid is utilized to introduce at least one precursor into a chamber during ALD, and in particular aspects the supercritical fluid is utilized to introduce multiple precursors into the reaction chamber during ALD. The invention can be utilized to form any of various materials, including metal-containing materials, such as, for example, metal oxides, metal nitrides, and materials consisting of metal. Metal oxides can be formed by utilizing a supercritical fluid can be utilized to introduce a metal-containing precursor into reaction chamber, with the precursor then forming a metal-containing layer over a surface of a substrate. Subsequently, the metal-containing layer can be reacted with oxygen to convert at least some of the metal within the layer to metal oxide.

RELATED PATENT DATA

This patent resulted from a continuation application of U.S. patentapplication Ser. No. 10/652,224, which was filed Aug. 22, 2003; andwhich is hereby incorporated by reference.

TECHNICAL FIELD

The invention pertains to methods of depositing materials oversubstrates and methods of forming layers over substrates. In particularaspects, the invention pertains to methods of forming layers associatedwith semiconductor constructions, such as, for example, methods offorming layers suitable for incorporation into semiconductor capacitordevices.

BACKGROUND OF THE INVENTION

There are numerous applications in which it is desired to form layersover substrates. For instance, it is frequently desired to form layersover semiconductor constructions during fabrication of integratedcircuitry. Among the methods commonly utilized for layer formation arechemical vapor deposition (CVD) processes and atomic layer deposition(ALD) processes.

ALD technology typically involves formation of successive atomic layerson a substrate. Such layers may comprise, for example, an epitaxial,polycrystalline, and/or amorphous material. ALD may also be referred toas atomic layer epitaxy, atomic layer processing, etc.

Described in summary, ALD includes exposing an initial substrate to afirst chemical species to accomplish chemisorption of the species ontothe substrate. Theoretically, the chemisorption forms a monolayer thatis uniformly one atom or molecule thick on the entire exposed initialsubstrate. In other words, a saturated monolayer. Practically, asfurther described below, chemisorption might not occur on all portionsof the substrate. Nevertheless, such an imperfect monolayer is still amonolayer in the context of this document. In many applications, merelya substantially saturated monolayer may be suitable. A substantiallysaturated monolayer is one that will still yield a deposited layerexhibiting the quality and/or properties desired for such layer.

The first species is purged from over the substrate and a secondchemical species is provided to chemisorb onto the first monolayer ofthe first species. The second species is then purged and the steps arerepeated with exposure of the second species monolayer to the firstspecies. In some cases, the two monolayers may be of the same species.Also, a third species or more may be successively chemisorbed and purgedjust as described for the first and second species. It is noted that oneor more of the first, second and third species can be mixed with inertgas to speed up pressure saturation within a reaction chamber.

Purging may involve a variety of techniques including, but not limitedto, contacting the substrate and/or monolayer with a carrier gas and/orlowering pressure to below the deposition pressure to reduce theconcentration of a species contacting the substrate and/or chemisorbedspecies. Examples of carrier gases include N₂, Ar, He, Ne, Kr, Xe, etc.Purging may instead include contacting the substrate and/or monolayerwith any substance that allows chemisorption byproducts to desorb andreduces the concentration of a species preparatory to introducinganother species. Purging time may be successively reduced to a purgetime that yields an increase in film growth rate. The increase in filmgrowth rate might be an indication of a change to a non-ALD processregime and may be used to establish a purge time limit.

ALD is often described as a self-limiting process, in that a finitenumber of sites exist on a substrate to which the first species may formchemical bonds. The second species might only bond to the first speciesand thus may also be self-limiting. Once all of the finite number ofsites on a substrate are bonded with a first species, the first specieswill often not bond to other of the first species already bonded withthe substrate. However, process conditions can be varied in ALD topromote such bonding and render ALD not self-limiting. Accordingly, ALDmay also encompass a species forming other than one monolayer at a timeby stacking of a species, forming a layer more than one atom or moleculethick. The various aspects of the present invention described herein areapplicable to any circumstance where ALD may be desired. It is furthernoted that local chemical reactions can occur during ALD (for instance,an incoming reactant molecule can displace a molecule from an existingsurface rather than forming a monolayer over the surface). To the extentthat such chemical reactions occur, they are generally confined withinthe uppermost monolayer of a surface.

The general technology of chemical vapor deposition (CVD) includes avariety of more specific processes, including, but not limited to,plasma enhanced CVD and others. CVD is commonly used to formnon-selectively a complete, deposited material on a substrate. Onecharacteristic of CVD is the simultaneous presence of multiple speciesin the deposition chamber that react to form the deposited material.Such condition is contrasted with the purging criteria for traditionalALD wherein a substrate is contacted with a single deposition speciesthat chemisorbs to a substrate or previously deposited species. An ALDprocess regime may provide a simultaneously contacted plurality ofspecies of a type or under conditions such that ALD chemisorption,rather than CVD reaction occurs. Instead of reacting together, thespecies may chemisorb to a substrate or previously deposited species,providing a surface onto which subsequent species may next chemisorb toform a complete layer of desired material.

Under most CVD conditions, deposition occurs largely independent of thecomposition or surface properties of an underlying substrate. Bycontrast, chemisorption rate in ALD might be influenced by thecomposition, crystalline structure, and other properties of a substrateor chemisorbed species. Other process conditions, for example, pressureand temperature, may also influence chemisorption rate. Accordingly,observation indicates that chemisorption might not occur appreciably onparticular portions of a substrate even though it occurs at a suitablerate on other portions of the same substrate.

A problem which can occur with CVD processes is that there is frequentlyless than 100% step coverage. ALD processes can frequently improve stepcoverage over CVD processes, but several difficulties are encounteredduring utilization of ALD processes.

One of the difficulties associated with ALD can occur in attempting todeliver sufficient flux of precursor within a reaction chamber forsuitable step coverage and uniformity. The difficulty can beparticularly severe when utilizing low vapor pressure precursormaterials (such as, for example, materials volatilized from solidsources), with low vapor pressure precursor materials typically beingunderstood to be materials having a vapor pressure of less than or equalto about 0.1 Torr at 100° C. Exemplary low vapor pressure precursormaterials include HfCl₄, TaF₅, and pentakis(dimethylamino)tantalum(PDMAT).

Other difficulties encountered in ALD include, for example, difficultiesassociated with the formation of mixed-material films (sometimesreferred to as doped films). For instance, it can be desired to formtitanium-doped tantalum pentoxide (Ta₂O₅) or aluminum-doped hafniumoxide (HfO₂). However, it can be difficult, and often seeminglyimpossible, to form a homogeneous film comprising low dopant levelsduring the monolayer-by-monolayer deposition of an ALD process. Forinstance, it can be desired for titanium-doped Ta₂O₅ to have about 8%TiO₂ incorporated within a Ta₂O₅ matrix. Such can theoretically beaccomplished by providing about twenty pulses of a tantalum precursor toone pulse of a titanium precursor during an ALD process. However, thematerial resulting from such process will typically have an atomic layerof TiO₂ sandwiched between thick Ta₂O₅ layers, and often the TiO₂ atomiclayer will not even be continuous. Accordingly, the film resulting fromseparate pulses of titanium and tantalum in an ALD process is not thedesired homogeneous mixture of TiO₂ and Ta₂O₅. Thus, it is desired todevelop new approaches for forming mixed materials utilizing ALDprocesses.

Although the invention was motivated at least in part by thedifficulties discussed above relative to ALD processes, it is to beunderstood that the invention has applications beyond addressing suchdifficulties. The invention is therefore not to be limited to theaddressing of such difficulties, or even to ALD processes, except to theextent that such limitations are expressly recited in the claims thatfollow.

SUMMARY OF THE INVENTION

In one aspect, the invention encompasses dispersal of a precursor in asupercritical fluid, introduction of the supercritical fluid/precursormixture into a reaction chamber, and formation of a monolayer over atleast a portion of a substrate surface utilizing the precursor.

In one aspect, the invention encompasses an atomic layer depositionmethod in which a first precursor is dispersed in a supercritical fluidand flowed into a reaction chamber to form a first component depositedover a surface of a substrate. A second precursor is flowed into thereaction chamber after the first precursor, and separately in time fromthe flowing of the first precursor into the reaction chamber. The secondprecursor forms a second component deposited over the surface of thesubstrate, and the first and second components together form a materialdeposited over the substrate. The material deposited over the substratecan be any of a number of materials, including, for example,metal-containing materials. The metal-containing materials can consistessentially of or consist of metal, or can be compounds containingnon-metals in addition to metals, such as, for example, metal nitridesand metal oxides. In particular aspects, the first precursor cancomprise a volatile metal-containing compound, the second precursor cancomprise oxygen, and the material formed from the first and secondprecursors can comprise a metal oxide. Exemplary metal oxides which canbe formed in accordance with methodology of the present inventioninclude tantalum oxides, titanium oxides, aluminum oxides and hafniumoxides.

In another aspect, the invention includes a method of forming a layerfrom at least two different precursors dispersed in a supercriticalfluid. The supercritical fluid having the precursors dispersed thereinis flowed into a reaction chamber and utilized to form a first materialcomprising components of the at least two precursors. After the firstmaterial is formed, substantially all of any of the at least twoprecursors remaining free within the chamber is removed, andsubsequently a reactant is flowed into the chamber to chemically convertat least some of the first material to a second material. In particularaspects, the first material can comprise hafnium and aluminum, and inother particular aspects the first material can comprise tantalum andtitanium. The reactant can comprise oxygen, and accordingly the secondmaterial can comprise, for example, aluminum oxide/hafnium oxide ortantalum oxide/titanium oxide.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a diagrammatic, cross-sectional view of an exemplary apparatusthat can be utilized for various treatments encompassed by exemplaryaspects of the present invention.

FIG. 2 is a diagrammatic, cross-sectional view of a semiconductor waferfragment being treated at a preliminary processing stage of an exemplarymethod of the present invention.

FIG. 3 is a view of the FIG. 2 wafer fragment being treated at aprocessing stage subsequent to that of FIG. 2.

FIG. 4 is a view of the FIG. 2 wafer fragment shown at a processingstage subsequent to that of FIG. 3.

FIG. 5 is a diagrammatic, cross-sectional view of a semiconductor waferfragment at a preliminary processing stage of a second embodiment methodof the present invention.

FIG. 6 is a view of the FIG. 5 wafer fragment shown being treated at aprocessing stage subsequent to that of FIG. 5.

FIG. 7 is a view of the FIG. 5 wafer fragment shown being treated at aprocessing stage subsequent to that of stage of FIG. 6.

FIG. 8 is a view of the FIG. 5 wafer fragment shown at a processingstage subsequent to that of FIG. 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

The invention includes various methods in which supercritical fluid isutilized to deliver one or more precursors into a reaction chamberduring a deposition process. The supercritical fluid can be any suitablesupercritical composition within which the precursor can be dispersed.Although the supercritical fluid can be a neat composition of precursor,typically it will not be. Instead, the supercritical fluid will comprisea composition other than that of the precursor, with an exemplarysupercritical fluid being a supercritical fluid comprising, consistingessentially of, or consisting of carbon dioxide.

As is known to persons of ordinary skill in the art, a supercriticalfluid is defined as any substance that is above its critical temperature(T_(c)) and critical pressure (P_(c)). T_(c) is the highest temperatureat which a gas can be converted to a liquid by an increase in pressure,and P_(c) is the highest pressure in which a liquid can be converted toa traditional gas by an increase in the liquid temperature. In theso-called critical region there is only one phase, and it possessesproperties of both gas and liquid. Supercritical fluids differ fromtraditional liquids in several aspects. For example, the “solvatingpower” of a supercritical fluid can frequently be controlled by changingtemperature and/or pressure to allow a wide variety precursor materialsto be dissolved.

For purposes of interpreting this disclosure and the claims that follow,the term “supercritical fluid” is utilized to refer specifically to aportion of a composition that is in a supercritical state (i.e., isutilized to refer to the supercritical component of a composition).Typically, the materials dispersed and/or dissolved within asupercritical fluid will not be in a supercritical state, andaccordingly will not be part of the supercritical fluid. However,precursors dispersed within a supercritical fluid can, in someinstances, be in a supercritical state.

Methodologies of the present invention can be utilized in variousdeposition processes, and in particular aspects will be utilized inatomic layer deposition processes. One of the challenges in conventionalALD is in delivering enough precursor to saturate the surface of thesubstrate quickly, preferably with a very square concentration pulse.Traditional ALD utilizes gas phase delivery of precursors, whichtypically provides the following limitations to the ALD process; (1) theconcentration of precursor attainable in the gas phase is limited, andcan be severely limited for precursors having a low vapor pressure(i.e., a vapor pressure of less than 0.1 Torr and 100° C.), also, theconcentration of precursor can be limited by the efficiency with whichgas delivery lines to a reaction chamber are heated, as improperlyheated delivery lines can result in condensation of precursor along thegas line walls in route to the chamber; and (2) the sharpness of theprecursor concentration pulse.

Particular aspects of the present invention can address both of theabove-described limitations of ALD processes by utilizing asupercritical fluid to enhance delivery of low-volativity precursors toa reaction chamber. Specifically, dissolving or otherwise dispersing oneor more low-volatility precursors in supercritical fluid can allowrelatively high concentrations of the precursors to be attained in agiven volume. Accordingly, supercritical fluid having one or moreprecursors dissolved therein can be introduced into a reaction chamberto obtain a relatively high concentration of precursor within thechamber. The high concentration of precursor can then be utilized in anALD process to form a monolayer over a substrate within the chamber.

Some aspects of the invention comprise maintaining a supercritical stateof the supercritical fluid within the reaction chamber during formationof the monolayer, and other aspects of the invention comprise releasingthe supercritical fluid from the supercritical state either during theflow of the supercritical fluid into the reaction chamber, or after adesired amount of precursor has been provided within the reactionchamber. In either event, the solubility of precursor within the fluidwill typically drop substantially as the fluid changes to anon-supercritical state, which can release a high concentration ofprecursor onto a substrate surface within the reaction chamber in ashort amount of time.

In a specific aspect of the invention, a desired volume of supercriticalfluid having one or more precursors dispersed therein is provided withina reaction chamber under conditions at which the supercritical fluid isin a supercritical state. The supercritical fluid is in a sense areservoir storing a desired amount of precursor within the reactionchamber. Subsequently, the conditions are changed so that the fluid isreleased from the supercritical state, which results in precursor beingreleased from the fluid. The released precursor forms ahigh-concentration pulse of precursor, which can, in preferredembodiments, correspond substantially to a desired square pulse ofprecursor in the ALD reaction chamber.

If the supercritical fluid utilized in a process of the presentinvention consists of CO₂, the critical pressure will be about 73atmospheres, and the critical temperature will be about 32° C. ALDreaction chambers can be configured to maintain such pressure andtemperature, and in particular aspects swagelock fittings can beutilized in connecting lines to the reaction chamber in order toaccommodate pressures suitable to maintain the supercritical state ofCO₂. The CO₂ critical temperature of 32° C. is actually lower thanprocess temperatures frequently utilized in ALD reaction chambers, andcan be easier to maintain than conventional ALD temperatures. Anadvantage of utilizing CO₂ as the supercritical solvent in methodologyof the present invention can be that CO₂ will generally not contaminatefilms formed utilizing such methodology as would other solvents, suchas, for example, hydrocarbon solvents.

Methodology of the present invention can be utilized with numerousprecursors, including, for example, precursors comprising one or moremetals. The metal-containing precursors can be utilized to formmaterials consisting of, or consisting essentially of metal; oralternatively can be utilized to form materials comprising metal andnon-metal elements, such as, for example, metal nitrides or metaloxides. In particular aspects, methodology of the present invention isutilized with aluminum-containing, hafnium-containing,tantalum-containing or titanium-containing precursors.

Exemplary aspects of the invention are described with reference to FIGS.1-8.

Referring initially to FIG. 1, such shows an apparatus 100 that can beutilized for an exemplary deposition process in accordance with anaspect of the present invention The apparatus 100 includes a reactionchamber 102. A wafer holder 104 is provided within the reaction chamber,and is shown supporting a wafer 12. An inlet 106 extends into chamber102 and an outlet 108 extends out of the chamber.

Reactant materials are flowed into chamber 102 through the inlet 106,with the direction of reactant material flow being exemplified by anarrow 110. The chamber is exhausted by removing materials from thechamber through outlet 108, with a direction of flow of removedmaterials being illustrated by arrow 112. A valve 114 is provided acrossinlet 106 for controlling flow of materials through the inlet, and avalve 116 is provided across outlet 108 for controlling flow ofmaterials through the outlet. A pump (not shown) can be provideddownstream of outlet 108 to assist in exhausting materials from withinreaction chamber 102.

Apparatus 100 can be utilized for either CVD processes or ALD processes.In an exemplary aspect, apparatus 100 is configured for utilization inan ALD process. In such aspect, two or more precursor compositions arealternately pulsed into the reaction chamber to deposit one or morelayers of material over substrate 12.

A pair of precursor compositions 120 and 122 are shown providedexteriorly of chamber 102 and in fluid communication with inlet 106through a valve 124. Valve 124 can be configured to selectively let onlyone of the precursor compositions 120 and 122 into chamber 102 at atime.

In operation, one of the precursor compositions 120 and 122 is flowedinto chamber 102 to a desired concentration within the chamber. Forpurposes of this discussion, precursor composition 120 will be referredto as the precursor composition which is first flowed into the reactionchamber. After composition 120 is flowed within the reaction chamber,precursor from the composition forms a monolayer over an exposed surfaceof substrate 12. Typically there will be excess precursor withinreaction chamber 102 so that some precursor remains free within thereaction chamber after the monolayer has been formed. The precursorwhich remains free within the chamber is substantially entirely flushedfrom within the chamber. Subsequently, the second precursor composition122 is flowed into chamber 102. The second precursor composition 122 isflowed into chamber 102 until a desired concentration of precursor fromsecond composition 122 is achieved within the reaction chamber. Theprecursor from composition 122 then interacts with the monolayer formedfrom the precursor of composition 120 to either form another monolayerover the first monolayer, or to chemically convert the composition ofthe first monolayer to a new composition. After a component fromprecursor 122 is formed over substrate 12, substantially all of theprecursor from composition 122 can be flushed (or in other words purged)from within chamber 102.

The term “substantially all” is utilized above to indicate that enoughof the free precursor is removed from within the reaction chamber toalleviate, and preferably prevent, chemical reaction from occurringbetween precursor of first composition 120 and precursor of secondcomposition 122 in any portion of chamber 102 except across the reactivesurface over substrate 12. Thus, precursors from compositions 120 and122 will be free in reaction chamber 102 at different and substantiallynon-overlapping times relative to one another in particular exemplaryALD applications of the present invention. Specifically, secondprecursor composition 122 can be considered to be flowed into chamber100 separately in time from first precursor composition 120 (and viceversa), in that the first and second precursor compositions are notprovided simultaneously within the reaction chamber. Such aspect of theinvention pertains to ALD processes. It is to be understood that theinvention can also have application to CVD processes, and in suchprocesses the first and second precursor compositions can be providedwithin reaction chamber 102 at the same time.

The alternating flow of precursor compositions 120 and 122 can be, inparticular aspects, considered a single iteration of an ALD process.Specifically, a single iteration of an ALD process for forming a depositover substrate 12 can comprise flowing first precursor composition 120into reaction chamber 102, purging first precursor composition 120 fromreaction chamber 102, flowing second precursor composition 122 intoreaction chamber 102, and purging second precursor composition 122 fromreaction chamber 102. Multiple iterations of such process can beperformed to form a desired material over substrate 12 to a desiredthickness.

One or both of precursor compositions 120 and 122 comprise one or moreprecursors dispersed in a supercritical fluid. In a particular aspect,first precursor composition 120 comprises one or more metal-containingprecursors dispersed in supercritical CO₂. At least one precursor withincomposition 120 can, for example, have a vapor pressure of less than orequal to about 0.1 Torr at 100° C., and the dispersal of such precursorwithin the supercritical fluid can allow a much higher concentration ofthe precursor to be obtained in a given volume than could occur withoutthe supercritical fluid. For instance, the concentration of precursorthat can be dissolved in supercritical fluid is frequently 1000 timesgreater than a concentration of precursor obtainable in gas phasewithout the supercritical fluid. Although the supercritical dispersionof various aspects of the invention can be particularly useful forlow-volatility precursors, the supercritical dispersion can also beuseful even for high volatility precursors. Specifically, dispersion ofprecursor in a supercritical fluid can enable formation of a moresaturated monolayer than a non-supercritical feed.

In particular aspects, the first precursor composition 120 comprises,consists essentially of, or consists of one or more suitablemetal-containing precursors (such as, for example, metal halide, ormetal organic materials) dispersed in a supercritical fluid comprising,predominately comprising, consisting essentially of, or consisting ofCO₂. Exemplary metals which can be utilized in the one or moreprecursors of composition 120 include hafnium, titanium, aluminum andtantalum.

As discussed previously, a supercritical fluid exists in thesupercritical state when critical conditions of pressure and temperatureare exceeded. If composition 120 comprises precursors disbursed insupercritical fluid, the supercritical state of the fluid can bemaintained as the fluid flows from a source of composition 120 to inlet106. Such can be accomplished by maintaining suitable pressure andtemperature along a passageway through which the composition 120 travelsto maintain the composition in the supercritical state.

Chamber 102 can be configured so that the conditions within the chamberare at or above the critical conditions of the supercritical fluid sothat the supercritical fluid is maintained in a supercritical state asthe fluid enters chamber 102. The fluid can thus function as a reservoirto maintain a desired a desired concentration of precursor within thereaction chamber. In such aspect of the invention, composition 120 isflowed into chamber 102 to the desired precursor concentration whilemaintaining the supercritical state of the fluid. Once the concentrationis achieved, the supercritical state of the fluid can continue to bemaintained while precursor interacts with a surface of substrate 12 toform a desired monolayer. In other aspects, one or more conditionswithin the reaction chamber can be changed and dropped below a criticalcondition so that the supercritical fluid transforms to anon-supercritical state within the reaction chamber. For instance, apressure within the reaction chamber can be dropped to below a criticalpressure to transform the supercritical fluid to a non-supercriticalstate.

As the fluid transforms to the non-supercritical state, the solventproperties of the fluid drop significantly (frequently by several ordersof magnitude) which can release a sharp pulse (i.e., high flux) ofnon-solvated precursor within chamber 102. Such sharp pulse of precursorcan enhance an ALD process of the present invention relative to priorart ALD processes.

In the processing described above, the supercritical state of asupercritical fluid is maintained as the fluid enters chamber 102. It isto be understood that the invention encompasses other aspects in whichthe chamber is configured so that a supercritical fluid transforms to anon-supercritical state as the fluid flows into the chamber. In otherwords, the chamber is operated so that one or more conditions in thechamber are below critical conditions of the supercritical fluid. Insuch aspects, the supercritical fluid is utilized to retain precursor insolution during transport of the precursor to the reaction chamber, butis not utilized as a reservoir for storing precursor within the reactionchamber.

Second precursor composition 122 can, alternatively or additionally tothe first precursor composition, comprise a precursor dispersed in asupercritical fluid. It can be particularly useful for composition 122to comprise a supercritical fluid in aspects in which a precursorutilized in composition 122 has low volatility.

In an exemplary process, first precursor 120 comprises a metal (such as,for example, one or more of hafnium, aluminum, tantalum or titanium) ina supercritical fluid, and is utilized to form a metal-containingmonolayer over a surface of substrate 12. Second precursor composition122 comprises an oxidant (such as, for example, one or moreoxygen-containing materials, which can include, for example H₂O and O₃)and is utilized for converting at least some of the metal of themetal-containing monolayer to oxide. In particular aspects, the secondprecursor composition (which can also be referred to as a reactantcomposition) is utilized for converting substantially all, or even all,of the metal of the metal-containing monolayer to metal oxide. Theoxidant of second precursor composition 122 is typically not dispersedin a supercritical fluid.

If composition 120 comprises a metal-containing precursor and isutilized to form a metal-containing monolayer, the metal formed in themonolayer can be referred to as being a metal-containing componentformed from the precursor of composition 120. Also, if the precursor ofcomposition 122 is an oxygen-containing precursor, an oxide formed fromreaction of the precursor from composition 122 with the metal-containinglayer can be referred to as containing an oxygen component from theprecursor of composition 122.

Reaction chamber 100 is described diagrammatically in FIG. 1, and it isto be understood that the reaction chamber can encompass numerousconfigurations in addition to those shown. For instance, precursors canbe introduced into reaction chamber 100 through a showerhead (notshown), and reaction chamber 100 can be configured so that an inert gasis flowed into chamber 102 during the purging of materials from thechamber, and/or during the flow of precursor compositions into thechamber.

An exemplary embodiment of the invention is described with reference toFIGS. 2-4. Referring initially to FIG. 2, a semiconductor wafer fragment10 is illustrated at a preliminary processing stage. Wafer fragment 10comprises a semiconductor substrate 12. Substrate 12 can comprise,consist essentially of, or consist of monocrystalline siliconlightly-doped with background p-type dopant. To aid in interpretation ofthe claims that follow, the terms “semiconductive substrate” and“semiconductor substrate” are defined to mean any constructioncomprising semiconductive material, including, but not limited to, bulksemiconductive materials such as a semiconductive wafer (either alone orin assemblies comprising other materials thereon), and semiconductivematerial layers (either alone or in assemblies comprising othermaterials). The term “substrate” refers to any supporting structure,including, but not limited to, the semiconductive substrates describedabove.

Substrate 12 has an upper surface 14, and is shown being treated with atreatment composition 20. Composition 20 forms a layer 18 over at leasta portion of upper surface 14, and in the shown aspect layer 18 isformed across an entirety of upper surface 14.

Treatment composition 20 comprises one or more appropriate precursors,and in particular aspects comprises the composition 120 described withreference to FIG. 1 (e.g., comprises one or more metal-containingprecursors dispersed in a supercritical fluid), or comprises one or moreprecursors released from a composition 120 that contained the one ormore precursors in combination with supercritical fluid.

Layer 18 can be considered to comprise at least a component of aprecursor from composition 20. In particular aspects, the component isonly a portion of the precursor while in other aspects the component isan entirety of the precursor.

Layer 18 can be a monolayer, and typically will be a monolayer if thetreatment of substrate 12 with composition 20 occurs in a true ALDprocess. The interaction of composition 20 with surface 14 to formmonolayer 18 can correspond to a physical interaction and/or a chemicalinteraction, and in particular aspects will correspond to chemisorption.

Composition 20 can comprise any suitable precursor which leads toformation of a desired layer 18. In particular aspects, layer 18 willcomprise a metal (i.e., will be a metal-containing layer), and in suchaspects the precursor comprises the metal desired in layer 18. Exemplarymetals which can be incorporated into the precursor, and ultimatelylayer 18, include aluminum, hafnium, titanium and tantalum. In specificaspects, the precursor of composition 20 can comprise, consistessentially of, or consist of one or more of titanium fluoride, titaniumisopropoxide, PDMAT, TaF₅, tantalum methoxide, and HfCl₄.

If treatment composition 20 comprises more than one precursor, thetreatment composition can be utilized to form a mixed metal layer 18. Inparticular aspects, the precursors within treatment composition 20comprise an aluminum-containing precursor and a hafnium-containingprecursor, and in some aspects the precursors within treatmentcomposition 20 consist essentially of, or consist of thealuminum-containing precursor and the hafnium-containing precursor. Insuch aspects, layer 18 can be formed to comprise, consist essentiallyof, or consist of aluminum and hafnium. In other aspects, the precursorswithin treatment composition 20 can comprise, consist essentially of, orconsist of a titanium-containing precursor and a tantalum-containingprecursor. In such aspects, layer 18 can be formed to comprise, consistessentially of, or consist of titanium and tantalum.

It can be desired that layer 18 contain tantalum doped with a smallamount of titanium. In such aspects, treatment composition 20 canconsist essentially of, or consist of titanium-containing precursor andtantalum-containing precursor, with the ratio of the titanium-containingprecursor to the tantalum-containing precursor being from about 5:95 toabout 10:90, and with an exemplary ratio being 8:92. Layer 18 can thenbe formed to comprise from about 5 atomic percent (atomic %) to about 10atomic % titanium, with the remainder being tantalum.

The precursors of treatment composition 20 are preferably provided tohigh concentration proximate surface 14 of substrate 12, and in a rapidpulse (i.e., are provided in a sharp concentration pulse, or in otherwords are provided in a relatively square concentration pulse). Such canbe accomplished by initially dispersing the precursors in asupercritical fluid, as described with reference to the apparatus 100 ofFIG. 1.

Referring next to FIG. 3, a second precursor composition 22 is utilizedto treat construction 10, and convert layer 18 (FIG. 2) to a layer 24.Second composition 22 can correspond to, for example, the precursorcomposition 122 described with reference to FIG. 1, or a precursorreleased from a composition containing precursor in supercritical fluid.In particular aspects, precursor composition 22 will comprise anoxidant. Precursor 22 can, for example, comprise, consist essentiallyof, or consist of one or both of O₃ and H₂O. The oxidant can be utilizedto treat a metal-containing layer 18 to convert metal of the layer tometal oxide. For instance, if layer 18 comprises, consists essentiallyof, or consists of one or more of hafnium, aluminum, titanium andtantalum; the layer 24 can comprise, consist essentially of, or consistof one or more of hafnium oxide, aluminum oxide, tantalum oxide andtitanium oxide. In other aspects, the precursor composition 22 cancomprising a nitridizing reagent, and can be utilized to convert metalof layer 18 to a metal nitride-containing material 24.

Referring to FIG. 4, construction 10 is illustrated after multipleiterations of the processing utilized to form layer 24 so that a stack30 containing several layers 24 is formed. The iterations of forminglayer 24 can be repeated until stack 30 reaches a desired thickness.Each of the layers 24 can be considered to be a material deposited oversubstrate 12 utilizing a single iteration of the processing describedwith reference to FIGS. 2 and 3. Such material can comprise, inparticular exemplary aspects, one or more metal oxides containing anoxygen component from precursor 22 and a metal component from precursor20; and in additional or alternative particular aspects one or moremetal nitrides containing a nitrogen component form precursor 22 and ametal component from precursor 20.

FIGS. 5-8 illustrate methodology of the present invention incorporatedinto an exemplary process of capacitor fabrication. Referring initiallyto FIG. 5, a semiconductor construction 40 comprises a substrate 42having an electrically insulative material 44 thereover. Substrate 42can comprise, for example, a monocrystalline silicon lightly-doped witha background p-type dopant. Insulative material 44 can comprise, forexample, borophosphosilicate glass (BPSG).

An electrically conductive pedestal 46 extends through insulativematerial 44. Pedestal 46 can comprise any suitable electricallyconductive material, including, for example, metal, metal compounds,and/or conductively-doped silicon. Pedestal 46 is connected to atransistor device 48. Specifically, pedestal 46 is ohmically connectedwith a source/drain diffusion region of the transistor device 48.

A conductive layer 50 is over pedestal 46 and electrically connectedwith pedestal 46. Conductive layer 50 can comprise any suitableconductive material or combination of materials, including, for example,metal, metal compounds and/or conductively-doped silicon.

Although substrate 42, insulative material 44 and conductive material 50are shown as homogeneous materials, it is to be understood that each ofthem can comprise multiple sub-components (not shown). For example,substrate 42 can comprise numerous levels of conductive and insulativematerials, insulative material 44 can comprise multiple layers ofinsulative materials, and conductive layer 50 can comprise multiplelayers of conductive materials.

Referring to FIG. 6, construction 40 is treated with a precursorcomposition 52 to form a layer 54 over the layer 50. Layer 54 is shownto be electrically conductive, and in particular aspects will comprisetwo or more metals. Layer 54 can be formed, for example, as a monolayerthrough ALD.

Precursor composition 52 contains a mixture of separate precursors. Twoseparate precursors 56 and 58 are shown diagrammatically in FIG. 6 asbeing combined to form the precursor composition 52. The individualprecursors 56 and 58 can be metal-containing precursors, with precursor56 comprising a different metal than does precursor 58.

In a particular aspect, precursor 56 can comprise aluminum and precursor58 can comprise hafnium. The ratio of aluminum to hafnium can be suchthat the metal-containing layer 54 is formed to have a smallconcentration of aluminum (less than 10 atomic %) within a hafniummaterial, so that the hafnium material is effectively aluminum-doped.

In another aspect, precursor 56 can comprise titanium and precursor 58can comprise tantalum. The ratio of the titanium-containing precursor tothe tantalum-containing precursor can be such that layer 54 is formed tohave less than about 10 atomic% titanium. For instance, layer 54 can beformed can be formed to have a ratio of titanium to tantalum of fromabout 5:95 to about 10:90 (by atomic %), and such ratio can be the sameas the ratio of titanium-containing precursor to tantalum-containingprecursor in the precursor composition 52. Suitable titanium-containingprecursors include, for example, titanium fluoride and titaniumisopropoxide; and suitable tantalum-containing precursors include TaF₅,tantalum ethoxide and TDMAT.

The precursors of composition 52 are preferably dispersed in asupercritical fluid prior to or during the treatment of FIG. 6, andaccordingly composition 52 can be utilized in methodology described withreference to FIG. 1. The supercritical fluid can comprise, consistessentially of, or consist of, for example, CO₂. In one exemplary aspectof the invention, precursor composition 52 can consist essentially ofsupercritical CO₂ having an aluminum-containing precursor and ahafnium-containing precursor dispersed therein. In another exemplaryaspect, precursor composition 52 can consist essentially ofsupercritical CO₂ having a titanium-containing precursor and atantalum-containing precursor dispersed therein. One of the advantagesof the present invention relative to prior art methodologies can be thatmultiple precursors can be mixed in a desired ratio in the precursorcomposition 52, and difficulties commonly associated with premixingprecursors in terms of matching vapor pressure and decompositiontemperature can be avoided utilizing the supercritical fluidmethodologies of the present invention.

If composition 52 comprises a supercritical fluid, the supercriticalfluid can, as discussed above with reference to FIG. 1, remain in asupercritical state during formation of layer 54, or can be released toa non-supercritical state within a reaction chamber to provide a pulseof precursor compositions utilized to form layer 54.

Although layer 54 is shown and described as containing at least twometals and as being formed from two or more metal-containing precursorsin the embodiment of FIG. 6, it is to be understood that the inventionincludes other aspects in which layer 54 is formed from only a singlemetal-containing precursor (or from two or more metal-containingprecursors which contain the same metal as one another) so that layer 54consists essentially of, or consists of a single metal. In particularaspects, layer 54 can be formed to comprise, consist essentially of, orconsist of one or more of hafnium, aluminum, titanium and tantalum.

If layer 54 is formed in a reaction chamber (such as the reactionchamber 102 described with reference to FIG. 1), some of the precursorutilized to form layer 54 can remain free within the reaction chamberafter formation of the layer. Substantially all of the free precursorcan then be removed from the reaction chamber, and subsequently layer 54can be treated with a reactant to convert at least some of the materialsof layer 54 to another material. In such aspect, layer 54 can bereferred to as comprising a first material, and at least some of thelayer can be considered to be chemically converted to a second material.In particular aspects, essentially all, or entirely all, of layer 54 isconverted to the second material.

FIG. 7 shows construction 40 as the metals of layer 54 (FIG. 6) aretreated with a reactant composition 60 to chemically convert layer 54 toa new material 62 (shown as an electrically insulative material).Reactant 60 can, for example, comprise oxygen, and can be utilized toconvert metals of layer 54 to metal oxides. Accordingly, if layer 54consists essentially of, or consists of titanium and tantalum, layer 62can consist essentially of, or consist of a mixture of tantalum oxideand titanium oxide. In particular aspects, the ratio of titanium oxideto tantalum oxide within layer 62 will be from about 5:95 to about10:90, with an exemplary ratio being about 8:92. An advantage ofprocessing the present invention relative to prior art methodologies isthat the titanium oxide will be dispersed uniformly without the tantalumoxide, rather than being laminarly interspersed relative to the tantalumoxide.

In another exemplary aspect of the invention, layer 54 can consistessentially of, or consist of aluminum and hafnium, and layer 62 canconsist essentially of, or consist of aluminum oxide and hafnium oxide.The aluminum oxide can be present to an atomic % of less than or equalto 10 atomic % and the hafnium oxide can be present to an atomic percentof greater than or equal to 90%. The aluminum oxide can be uniformlydistributed throughout the hafnium oxide.

Layer 62 can be utilized as a dielectric material in a capacitorconstruction. Such is illustrated in FIG. 8. Specifically, a secondconductive material 64 is formed over dielectric material 62, and spacedfrom first conductive material 50 by the dielectric material 62. Firstconductive material 50 can be considered to be a first capacitorelectrode, second conductive material 64 can be considered to be asecond capacitor electrode, and dielectric material 62 can be consideredto be a capacitor dielectric separating electrodes 50 and 64 from oneanother. Although second electrode 64 is shown formed directly againstdielectric material 62, it is to be understood that the inventionincludes other aspects (not shown) in which one or more additionaldielectric materials are formed over dielectric material 62 prior toformation of second electrode 64.

The capacitor construction comprising materials 50, 62 and 64 can beincorporated into a DRAM device. Specifically, the capacitorconstruction can be connected to a first source/drain region oftransistor device 48, a gate (not shown) of the transistor device can beconsidered to be a wordline, and a second source/drain region of thetransistor device can be connected to a bitline (not shown).

The shown capacitor construction comprising materials 50, 62 and 64 isbut one of many capacitor constructions that can be formed utilizingmethodology of the present invention. Other capacitor constructions canhave other shapes, including, for example, container shapes. Also, it isto be understood that a capacitor device is but one exemplary devicethat can be formed utilizing methodology of the present invention, andother devices can also be formed utilizing such methodology.

The invention can be utilized for numerous applications. For instance,methodology of the present invention can form porous films, with desired“doping”, while alleviating and even avoiding contamination fromsolvents that would otherwise be utilized in prior art methodologies.Materials formed in accordance with methodology of the present inventioncan be patterned (via, for example, a selective etch) in furtherprocessing (not shown).

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A method of forming a layer over a substrate, comprising: providing a reaction chamber having a substrate therein, the substrate having a surface; and atomic layer depositing a material comprising aluminum and hafnium, the atomic layer depositing comprising flowing an aluminum-containing precursor into the reaction chamber, and flowing an a hafnium-containing precursor into the reaction chamber; the precursors being dispersed within supercritical fluid as the precursors are flowed into the reaction chamber.
 2. The method of claim 1 wherein the precursors are together flowed into reaction chamber as a mixture.
 3. The method of claim 1 wherein the precursors are flowed into reaction chamber sequentially relative to one another.
 4. A method of depositing material over a semiconductor substrate, comprising: providing a first precursor and a second precursor different from the first precursor; providing an atomic layer deposition reaction chamber having a semiconductor substrate therein, the semiconductor substrate having a surface; performing at least one iteration of the following sequence in the following order: flowing the first precursor into the chamber to form a first component monolayer deposited over a surface of the semiconductor substrate; purging the chamber; flowing the second precursor into the chamber to form a second component over the surface of the semiconductor substrate; and purging the chamber; and wherein: at least one of the first and second precursors is dispersed in a supercritical fluid as it is flowed into the reaction chamber; the first precursor comprises a metal; the first component monolayer comprises the metal; the second precursor comprises oxygen; the second component comprises the oxygen; the first precursor is part of a mixture of precursors; the precursors within the mixture comprise two or more different metals; the first component monolayer comprises the two or more different metals; and the mixture of precursors contains an aluminum-containing precursor and a hafnium-containing precursor.
 5. A method of depositing material over a semiconductor substrate, comprising: providing a first precursor and a second precursor different from the first precursor; providing an atomic layer deposition reaction chamber having a semiconductor substrate therein, the semiconductor substrate having a surface; performing at least one iteration of the following sequence in the following order: flowing the first precursor into the chamber to form a first component monolayer deposited over a surface of the semiconductor substrate; purging the chamber; flowing the second precursor into the chamber to form a second component over the surface of the semiconductor substrate; and purging the chamber; and wherein: at least one of the first and second precursors is dispersed in a supercritical fluid as it is flowed into the reaction chamber; the first precursor comprises a metal; the first component monolayer comprises the metal; the second precursor comprises oxygen; the second component comprises the oxygen; the first precursor is part of a mixture of precursors; the precursors within the mixture comprise two or more different metals; the first component monolayer comprises the two or more different metals; the mixture of precursors contains a titanium-containing precursor and a tantalum-containing precursor; and a ratio of the titanium-containing precursor to the tantalum-containing precursor is from about 5:95 to about 10:90, by atomic percent.
 6. A method of forming a layer over a semiconductor substrate, comprising: providing a supercritical fluid comprising at least two different precursors dispersed therein; providing a reaction chamber having a semiconductor substrate therein, the semiconductor substrate having a surface; flowing the supercritical fluid into the reaction chamber and forming a first material comprising components of the at least two different precursors; after forming the first material, purging the chamber; after the purging, flowing a reactant into the chamber to chemically convert at least some of the first material to a second material; wherein one of the at least two different precursors comprises hafnium and another of the at least two different precursors comprises aluminum; and wherein the first material comprises hafnium from said one of the precursors and aluminum from said other of the precursors.
 7. The method of claim 6 wherein the first material consists essentially of the hafnium and the aluminum.
 8. A method of forming a layer over a semiconductor substrate, comprising: providing a supercritical fluid comprising at least two different precursors dispersed therein; providing a reaction chamber having a semiconductor substrate therein, the semiconductor substrate having a surface; flowing the supercritical fluid into the reaction chamber and forming a first material comprising components of the at least two different precursors, the first material being formed over at least a portion of the surface of the substrate; after forming the first material, purging the chamber; after the purging, flowing a reactant into the chamber to chemically convert at least some of the first material to a second material; wherein one of the at least two different precursors comprises titanium and another of the at least two different precursors comprises tantalum; wherein the first material comprises titanium from said one of the precursors and tantalum from said other of the precursors; and wherein a ratio of said one of the precursors to said other of the precursors within the supercritical fluid is from about 5:95 to about 10:90.
 9. The method of claim 8 wherein a ratio of titanium to tantalum within the first material is from about 5:95 to about 10:90. 